1. Field of the Invention
The invention relates to a data carrier which is designed for the communication of transmission data with a base station in which power consumers of the data carrier can be deactivated over certain time ranges.
The invention further relates to a circuit of a data carrier as defined in the first paragraph.
The invention further relates to a method of temporarily deactivating power consumers of a data carrier as described in the first paragraph.
2. Description of Related Art
The document U.S. Pat. No. 5,286,955 discloses a base station which is designed for the transmission of transmission data to a data carrier over a transmission time range. For this purpose the base station emits an electromagnetic carrier field which is received in the data carrier and from which the data carrier generates a carrier signal.
The base station, however, transmits the electromagnetic carrier field only over on-periods contained in the transmission time range and not over off-periods contained in the transmission time range. If the data carrier detects 16-23 cycles of the carrier signal in an on-time range contained between off-periods, the data carrier decodes a bit xe2x80x9c1xe2x80x9d of the transmission data, and if the data carrier detects 8-15 cycles in an on-period contained between off-time ranges, the data carrier a decodes a bit xe2x80x9c0xe2x80x9d of the transmission data transmitted from the base station to the data carrier.
The data carrier has power generating means for the generation and storage of a DC power from the carrier signal received, the DC power being used for operation of the passive data carrier. Since the power generating means of the known data carrier cannot generate a DC power over the off-time ranges, the data carrier has a voltage detector which detects the fall in the amplitude of the carrier signal. When the amplitude of the carrier signal has fallen below a cut-off threshold, the voltage detector deactivates clock signal generating means of the known data carrier, so that the power consumption of the data carrier is substantially reduced in a reception mode of the data carrier.
Whilst the clock signal generating means of the data carrier are deactivated, the data carrier is supplied from a storage capacitor charged during the on-time ranges. When the amplitude of the carrier signal at the start of the on-period is once more greater than the cut-off threshold, the voltage detector again activates the clock signal generating means, so that the known data carrier continues the decoding of the transmission data to be received.
Were the known data carrier to be similarly operated in a transmission mode for the transmission of transmission data to the base station, the same disadvantage would occur in the transmission mode as in the reception mode, namely that the power consumption of the data carrier would not be reduced immediately at the start of each off-period but only with a time delay once the carrier signal had already fallen below the cut-off threshold. As a result, some of the DC power stored in the storage capacitor would already be consumed before deactivation of the principal power consumers of the data carrier, so that the storage capacitor would have to be designed with a relatively large capacitance, which is very disadvantageous especially in the case of an integrated circuit.
It is an object of the invention is create a data carrier of the generic type specified in the first paragraph, a circuit of the generic type specified in the second paragraph and a method of the generic type specified in the third paragraph in which the aforementioned disadvantages in the transmission mode of the data carrier are avoided.
To achieve the aforementioned object, features according to the invention are provided in such a data carrier, so that the data carrier can be characterized as specified below.
A data carrier for the transmission of transmission data to a base station over a transmission time range containing load time ranges and load relief time ranges, having receiving means for the reception of a carrier signal from an electromagnetic carrier field and having power generating means for the generation and storage of a DC power from the carrier signal received, the DC power being used for operation of the passive data carrier, and having data processing means for the processing and output of the transmission data to be transmitted and having transmission means for transmission of the transmission data to the base station over the transmission time range, the electromagnetic carrier field being subjected to a load by the transmission means over the load time ranges, so that over the load time ranges the amplitude of the carrier signal received is essentially less than over the load relief time ranges and the data carrier is operated over the load time ranges essentially with the stored DC power, cut-off means being provided which are designed to deactivate at least one power consumer of the data carrier at a cut-off time defined by the data processing means or by the transmission means immediately prior to or at the start of each load time range and which are designed to reactivate the deactivated power consumers once a cut-off time range following the cut-off time has elapsed.
To achieve the aforementioned object, features according to the invention are provided in such a circuit, so that the circuit can be characterized as specified below.
A circuit for a data carrier for the transmission of transmission data to a base station, the circuit being of integrated design and the circuit with antenna means connected forming the data carrier according to the paragraph above.
To achieve the aforementioned object, features according to the invention are provided in such a method, so that the method can be characterized as specified below.
A method of transmitting transmission data from a data carrier to a base station over a transmission time range containing load time ranges and load relief time ranges, comprising the following stages: reception of a carrier signal from an electromagnetic carrier field; generation and storage of a DC power from the carrier signal received, said DC power being used for operation of the passive data carrier; processing and output of the transmission data to be transmitted; transmission of the transmission data to the base station over the transmission time range, the electromagnetic carrier field being subjected to a load by the transmission means over the load time ranges, so that over the load time ranges the amplitude of the carrier signal received is essentially less than over the load relief time ranges and the data carrier is essentially operated by means of the stored DC power over the load time ranges, at least one power consumer of the data carrier being deactivated at a fixed cut-off time immediately prior to or at the start of each load time range, and the deactivated power consumer being reactivated once a cut-off time range following the cut-off time has elapsed.
As a result, the cut-off means have already substantially reduced the power consumption of the passive data carrier immediately prior to the actual fall in the carrier signal over the load time range. This affords the advantage that a DC power storage device (storage capacitor) provided for operation of the data carrier in the transmission mode over the load time ranges can have a relatively low capacitance, since whilst the amplitude of the carrier signal is falling at the start of the load time range, principal power consumers of the data carrier are already deactivated and consume virtually no DC power.
The measures as claimed in claims 2, 3 and 8 afford the advantage that the largest power consumers of the data carrier consume no DC power over the load time ranges of the transmission mode owing to the deactivation of the clock signal generating means and/or the data processing means by the cut-off means.
The provision of the timer element in the cut-off means for determining the duration of the cut-off time range affords the advantage that the clock signal generating means of the data carrier, which according to the state of the art are necessary for determining time ranges, can be deactivated over the load time ranges, so that a principal power consumer consumes no power over the load time ranges. In addition, the measures as claimed in claim 4 afford the advantage that the cut-off means can be provided in a particularly simple and inexpensive way, making it possible to incorporate the cut-off means in an integrated circuit.
The measures as claimed in claim 5 afford the advantage that the electromagnetic carrier field is subjected to particularly heavy loading by the data carrier, thereby permitting a reliable decoding of the transmission data in the base station.
The measures as claimed in claims 6, 9 and 11 afford the advantage that the cut-off time range, possibly modified owing to component tolerances, can be periodically calibrated. Components with larger tolerance ranges can thus be used for the timer element, making the data carrier inexpensive to produce.